The invention relates to spinal osteosynthesis systems, in particular for anterior fixation.
Spinal osteosynthesis systems for anterior fixation are known in which the connection element is formed by a plate, and others are known in which the connection element is formed by a rod. Because of their bulk, the plate systems are difficult to use, if they can be used at all, via the endoscopic route. Moreover, their limited size (length) means that they can only be used for simple vertebrectomies involving a single vertebra, or perhaps two. It is impossible to treat scoliosis with this type of system. Finally, a plate is difficult to adapt to the morphology of the vertebrae in which it is anchored. Moreover, the rod systems generally comprise fairly voluminous connectors which cannot always be used via the endoscopic route.
A spinal osteosynthesis device is also known from U.S. Pat. No. 5,938,663, which device comprises a clamp or connector with two branches which can clamp a connection rod between them, the branches being able to be engaged on a vertebral pedicle screw. The rod is received between the branches with interposition of a slotted ring which has a spherical face and is engaged on the rod in order to control the angular orientation of the connector relative to the rod before clamping. However, this device, while well suited for posterior fixation of the spine on the vertebral pedicles, does not always provide sufficient rigidity with a view to anterior fixation of the spine.
An object of the invention is to make available a different spinal osteosynthesis system, adapted for anterior fixation, easy to fit, ensuring good rigidity of the system on the spine, and compatible with being fitted via the endoscopic route.
To achieve this object, the invention provides a spinal osteosynthesis system, in particular for anterior fixation, comprising at least one anchoring member, an elongate connection element and a connector which is able to be fixed to the anchoring member and to the connection element by choosing an angular position of the connection element relative to the connector, the system comprising a second elongate connection element, the connector being able to be fixed simultaneously to the two connection elements.
Thus, the presence of the two connection elements gives the system very great rigidity, without complicating its assembly, without increasing the volume of its various components (which renders it compatible with fitting via the endoscopic route), and while maintaining the possibility of controlling the angular position of the connector relative to the first connection element. The system according to the invention does not require identical bending on the two connection elements. Moreover, the number of connectors can remain small.
Advantageously, the system is designed in such a way that the second connection element can be fixed to the connector only in a single angular position relative to the connector.
Thus, the shape of the second connection element dictates the relative angular position of the connectors which are fixed to it. This angular position can therefore be chosen in advance depending on the prior curvature given to this connection element, either at the time of manufacture or, better still, during the surgical intervention.
Advantageously, the second connection element has less resistance to bending than the first connection element.
Thus, the first connection element has mainly a function ensuring support of the connectors, and the second connection element has mainly a function ensuring angular positioning of the connectors.
Advantageously, the connector comprises two branches which can clamp at least one of the two connection elements.
Advantageously, the branches have first ends via which they are connected to each other and second free ends.
This simplifies production of the connector. Moreover, by appropriately selecting the flexibility of the connector and/or the diameter of the second connection element, this element can be introduced laterally between the free ends of the branches, which makes fitting easier.
Advantageously, the connector is able to receive the second connection element by lateral insertion between the free ends.
Advantageously, the branches can simultaneously clamp the two connection elements.
Advantageously, the anchoring member comprises a vertebral screw, at least a first of the two branches being able to be engaged on the screw.
Advantageously, the vertebral screw has a threaded orifice, the system comprising a clamping screw which can constitute a screw-nut connection with this orifice and is able to bear on one of the branches in order to clamp the branches.
Advantageously, the system comprises a second vertebral screw, the first branch being able to be engaged simultaneously on the two vertebral screws.
Advantageously, the system is designed in such a way that the second connection element, when fixed to the connector, extends in a trajectory of the second vertebral screw for its disengagement from the connector.
Thus, the second screw is prevented from starting to come out at an inopportune moment.
Advantageously, the system comprises a ring which can be engaged on the first connection element and received between the branches in order to choose the angular position of the first connection element before the branches are clamped.